Stabilized expandable intervertebral spacer

ABSTRACT

A spacer for separating bones of a joint, the spacer includes a first endplate configured to engage a first bone of the joint, and comprising a ramped surface; a tissue engaging subassembly disposed in a compartment of the first endplate; a second endplate configured to engage a second bone of the joint; and a frame subassembly that extends between the first endplate and the second endplate. The frame subassembly comprises a drive nut, a drive shaft coupled to the drive nut, a ramped carriage coupled to the drive shaft, wherein the ramped carriage comprises a ramped surface operable to engage the ramped surface of the first endplate, and an actuation bar coupled to the drive nut comprising a plate operable to engage the tissue engaging subassembly.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral spacer, and more particularly anintervertebral spacer that is stabilized and adjustable in height.

BACKGROUND

The vertebral or spinal column (spine, backbone) is a flexible assemblyof vertebrae stacked on top of each other extending from the skull tothe pelvic bone which acts to support the axial skeleton and to protectthe spinal cord and nerves. The vertebrae are anatomically organizedinto four generalized body regions identified as cervical, thoracic,lumbar, and sacral; the cervical region including the top of the spinebeginning in the skull, the thoracic region spanning the torso, thelumbar region spanning the lower back, and the sacral region includingthe base of the spine ending with connection to the pelvic bone. Withthe exception of the first two cervical vertebrae, cushion-like discsseparate adjacent vertebrae, i.e. intervertebral discs.

The stability of the vertebral column during compression and movement ismaintained by the intervertebral discs. Each disc includes a gel-likecenter surrounded by a fibrous ring. The gel-like center, i.e. nucleuspulposus, provides strength such that the disc can absorb and distributeexternal loads and contains a mixture of type II-collagen dispersed in aproteoglycan matrix. The fibrous ring, or annulus fibrosus, providesstability during motion and contains laminated rings of type-I collagen.Thus, the annulus fibrosis and the nucleus pulposus are interdependent,as the annulus fibrosis contains the nucleus pulposus in place and thenucleus pulposus aligns the annulus fibrosus to accept and distributeexternal loads. The integrity of the composition and structure of theintervertebral disc is necessary to maintain normal functioning of theintervertebral disc.

Many factors can adversely alter the composition and structure of theintervertebral disc, such as normal physiological aging, mechanicalinjury/trauma, and/or disease, resulting in impairment or loss of discfunction. For example, the content of proteoglycan n the nucleuspulposus declines with age, thus, it follows that the ability of thenucleus pulposus to absorb water concurrently declines. Therefore, innormal aging the disc progressively dehydrates, resulting in a decreasein disc height and possible de-lamination of the annulus fibrosus.Mechanical injury can tear the annulus fibrosis allowing the gel-likematerial of the nucleus pulposus to extrude into the spinal canal andcompress neural elements. Growth of a spinal tumor can impinge upon thevertebrae and/or disc potentially compressing nerves.

Bones of the spine, and bony structures, generally, are susceptible to avariety of weaknesses that can affect their ability to provide supportand structure. Weaknesses in bony structures have numerous potentialcauses, including degenerative diseases, tumors, fractures, anddislocations. Advances in medicine and engineering have provided doctorswith a plurality of devices and techniques for alleviating or curingthese weaknesses.

In some cases, the spinal column, in particular, requires additionalsupport in order to address such weaknesses. One technique for providingsupport is to insert a spacer between adjacent vertebrae.

SUMMARY

In accordance with an embodiment of the disclosure, a spacer forseparating bone of a joint may be provided. The spacer may comprise afirst endplate configured to engage a first bone of the joint, andcomprising a ramped surface; a tissue engaging subassembly disposed in acompartment of the first endplate; a second endplate configured toengage a second bone of the joint; and a frame subassembly that extendsbetween the first endplate and the second endplate. The framesubassembly comprises a drive nut, a drive shaft coupled to the drivenut, a ramped carriage coupled to the drive shaft, wherein the rampedcarriage comprises a ramped surface operable to engage the rampedsurface of the first endplate, and an actuation bar coupled to the drivenut comprising a plate operable to engage the tissue engagingsubassembly.

In accordance with an embodiment of the disclosure, another spacer forseparating bone of a joint may be provided. The spacer may comprise afirst endplate configured to engage a first bone of the joint, whereinthe first endplate comprises a pair of spaced first endplate rampedsurfaces. The spacer may comprise a first pair of tissue engagingsubassemblies, wherein each of the tissue engaging subassemblies arepivotally coupled to the first endplate. The spacer may comprise asecond endplate configured to engage a second bone of the joint, whereinthe second endplate comprises a pair of spaced second endplate rampedsurfaces. The spacer may comprise a second pair of tissue engagingsubassemblies, wherein each of the tissue engaging subassemblies arepivotally coupled to the first endplate. The spacer may comprise a framesubassembly that extends between the first endplate and the secondendplate. The frame subassembly comprise a drive nut at a proximate endof the spacer, wherein the drive nut comprises a head portion and anextension, wherein the extension comprises a threaded portion. The framesubassembly may comprise a drive shaft extending from the drive nuttowards a distal end of the spacer, wherein a proximal end of the driveshaft is retained in a through bore of the drive nut. The framesubassembly may comprise a pair of ramped carriages that are spaced andthreadingly coupled to the drive nut, wherein each of the rampedcarriages comprises ramped surfaces operable to engage the secondendplate ramped surfaces and the second endplate ramped surfaces. Theframe subassembly may comprise an actuation bar coupled to the driveshaft. The actuation bar may comprise a base plate threadingly coupledto the threaded portion of the drive nut. The actuation bar may comprisea pair of opposing arms that extend from the base plate toward a distalend of the spacer, the opposing arms extending through the rampedcarriages. The actuation bar may comprise plates disposed in spacedslots formed in each of the opposing arms of the actuation bar, whereinthe plates are operable to engaging the first pair of tissue engagingsubassemblies and the second pair of tissue engaging subassemblies.

In accordance with an embodiment of the disclosure, a method ofseparating bones of a joint may be provided. The method may compriseinserting a spacer between bones of the joint. The method may compriserotating a drive shaft of the spacer to cause translation of at leastramped carriage disposed on the drive shaft, wherein the at least oneramped carriage slides along at least one ramped surface of a firstendplate of the spacer to cause the first endplate to move in adirection away from a second endplate of the spacer. The method maycomprise rotating a drive nut of the spacer to cause translation of abar subassembly disposed between the first endplate and the secondendplate such that at least one plate coupled to the frame engages atleast one tissue engaging subassembly to cause the at least one tissueengaging subassembly to deploy through the first endplate.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some examples of thepresent invention, and should not be used to limit or define theinvention.

FIG. 1 is a perspective view of a spacer of the disclosure in acollapsed position;

FIG. 2 is a perspective view of the spacer of FIG. 1 in an expandedposition;

FIG. 3 is a perspective view of the spacer of FIG. 1 with body tissueengaging projections deployed;

FIGS. 4 and 5 illustrate an actuation frame subassembly of the spacer ofFIG. 1;

FIG. 6 is an exploded view of an actuation frame subassembly of thespacer of FIG. 1;

FIG. 7 illustrates a drive subassembly of the spacer of FIG. 1;

FIG. 8 illustrates an exploded view of a drive subassembly of the spacerof FIG. 1;

FIG. 9 is a cutaway view of a drive screw of the drive subassembly ofFIG. 7;

FIG. 10 is a cutaway view of a retainer block of the drive subassemblyof FIG. 7;

FIG. 11 illustrates a projection actuation bar of the drive subassemblyof FIG. 7;

FIG. 12 is a cutaway view of a projection actuation bar of the drivesubassembly of FIG. 7;

FIGS. 13 and 14 are alternate views of an endplate of the spacer of FIG.1;

FIG. 15 is a cutaway view of an endplate of the spacer of FIG. 1;

FIG. 16 is an exploded view of an endplate subassembly of the spacer ofFIG. 1;

FIG. 17 illustrates an endplate subassembly of the spacer of FIG. 1;

FIG. 18 illustrates a body tissue engaging projection subassembly of thespacer of FIG. 1;

FIG. 19 is an exploded view of a body tissue engaging projectionsubassembly of the spacer of FIG. 1;

FIG. 20 illustrates a base of the body tissue engaging projectionsubassembly of FIG. 18;

FIG. 21 illustrates positioning of the actuation frame subassembly withthe endplate subassembly;

FIG. 22 illustrates positioning the endplate subassembly assembled withthe actuation frame subassembly;

FIG. 23 is a side view of the spacer of FIG. 1 in a collapsed position;

FIG. 24 is a cutaway view of the spacer of FIG. 1 in a collapsedposition;

FIG. 25 is a perspective view of the spacer of FIG. 1 in an expandedposition;

FIG. 26 is a side view of the spacer of FIG. 1 in an expanded position;

FIGS. 27 and 28 are cutaway views of the spacer of FIG. 1 in an expandedposition;

FIG. 29 is a perspective view of the spacer of FIG. 1 with body tissueengaging projections deployed;

FIG. 30 is a side view of the spacer of FIG. 1 with body tissue engagingprojections deployed;

FIGS. 31 and 32 are cutaway views of the spacer of FIG. 1 with bodytissue engaging projections deployed;

DETAILED DESCRIPTION

With reference to FIGS. 1-3, the disclosure provides a spacer 100 thatis stabilized and has an adjustable height. The spacer is insertedbetween two adjacent bony surfaces to facilitate separation of thebones, and if desired, to promote the fusion of bony surfaces. Althoughintended to be useful with any adjacent bony surface in which fusion isdesired, the spacer 100 is advantageously applied to insertion betweentwo adjacent vertebral bodies in any section of the spine, including thecervical, thoracic, lumbar, and sacral vertebral sections. More than onespacer 100 may be implanted within the body, for example betweensuccessive or separated vertebrae, between adjacent vertebrae. The useof multiple spacers 100 is particularly advantageous for patients whoseback pain is not limited to a localized area, or for patients whoselocalized damage has progressed to other areas of the spine.

The spacer 100 and methods for its insertion can be used in a treatmentprotocol for any of a wide variety of conditions in a patient involvingdiseased or damaged bony structures. The patient can be a human being.Additionally, it is contemplated that the spacer 100 may be useful inveterinary science for any animal having adjacent bony structures to befused. The spacer 100 can collapse, for example, to approximately onehalf of an expanded size, as illustrated on FIG. 1, for example. When inthis collapsed configuration, the spacer 100 can be inserted into aspace through a small incision and narrow pathways, using appropriateminimally-invasive techniques, and can be positioned within the spacebetween adjacent bones, and there expanded to a desired therapeuticheight, as illustrated on FIG. 2, for example. The incision may beshort, for example about one inch in length, which is smaller than thespacer 100 in an expanded configuration. If the desired position and/orexpansion are not achieved, the spacer 100 can be collapsed,repositioned, and re-expanded in situ. Additionally, body tissueengaging projections 118 may be retracted during insertion and expansionof spacer 100. After the spacer 100 has been inserted and expanded, bodytissue engaging projections 118 may be deployed, as shown on FIG. 3, forexample.

Although the spacer 100 is exemplified herein for use in the spine, thespacer 100 is contemplated for fusion of any bony structures. While thespacers 100 are described herein using several varying embodiments, thespacers 100 are not limited to these embodiments. An element of oneembodiment may be used in another embodiment, or an embodiment may notinclude all described elements.

With continued reference to FIGS. 1-3, embodiments of spacer 100 mayinclude endplates 102, 104 having expansion ramps 106 mateable withmoveable ramped carriages 108 on actuation frame subassembly 110. In theembodiment shown, endplates 102, 104 are symmetrical, and spacer 100 canbe implanted with either endplate positioned superior with respect tothe other. In other embodiments, they may be dissimilar, and aparticular orientation may then be advantageous or necessary.

Spacer 100 forms a distal end 112 which may be inserted first into thebody, and which can be tapered to facilitate insertion between bodytissue, and a proximal end 114, to which a tool may be connected. Spacer100 may be inserted into the body in a collapsed position shown onFIG. 1. Distal and proximal ends 112 and 114 define a longitudinal axis116, extending therebetween. To expand spacer 100, ramped carriages 108may be displaced relative to endplates 102, 104 causing expansion ramps106 to slide along ramped carriages 108, thereby moving endplates 102,104 relatively apart such that a height of spacer 100 may be increased.FIG. 2 illustrates the spacer 100 in an expanded position. As seen onFIG. 3, spacer 100 further includes body tissue engaging projections118. The body tissue engaging projections 118 may be retracted duringinsertion and expansion of spacer 100. After the spacer 100 has beeninserted and expanded, body tissue engaging projections 118 may bedeployed. The body tissue engaging projections 118 may be deployed toengage adjacent tissue (e.g., endplates), for example, to fixate thespacer 100 in place. Advantageously, engagement of adjacent tissue withbody tissue engaging projections 118 may prevent migration and/ortipping spacer 100 prior to fusion occurring.

Turning now to FIGS. 4-6, actuation frame subassembly 110 is illustratedin more detail in accordance with embodiments of the present disclosure.Actuation frame subassembly 110 may extend between endplates 104, 104.As illustrated, actuation frame subassembly 110 may comprise rampedcarriages 108, drive subassembly 120, projection actuation bar 122, andretainer blocks 124. In the illustrated embodiment, drive subassembly120 comprises drive nut 126 and drive shaft 128. Ramped carriages 108may be displaced relative to endplates 102, 104 (e.g., shown on FIGS.1-3) by rotation of drive shaft 128. In some embodiments, rotation ofdrive shaft 128 may cause ramped carriages 108 to translate a path alonglongitudinal axis 116 of spacer 100. Ramped carriages 108 may each havea through bore 130 (best seen on FIG. 6) which may be threadedly coupledto a threaded portion 132 of drive shaft 128. Ramped carriages 108 mayeach comprise ramped surfaces 109 that engage the correspondingexpansion ramps 106 of endplates 102, 104 (e.g., shown on FIG. 103). Insome embodiments, each ramped carriage 108 may comprise a pair of rampedsurfaces 109 on opposite sides of the ramped carriage 108. In someembodiments, one or more guide elements (e.g., guide pins 134 on FIGS.4-7) may be provided to prevent endplates 102, 104 from moving alonglongitudinal axis 116 along with ramped carriages 108, thereby causingramped carriages 108 and expansion ramps 106 to be moved relative to oneanother, expanding or contracting spacer 100. While FIGS. 4-6 illustrateguides pins 134 as one-piece pins, each of guide pins 134 may bemulti-piece.

In some embodiments, projection actuation bar 122 may comprise baseplate 136 and arms 138. In the illustrated embodiment, arms 138 extendfrom base plate 136 in the direction of distal end 112 of spacer 100. Asillustrated, arms 138 may extend substantially parallel and be generallyopposed to one another. In some embodiments, arms 138 may extend throughcorresponding through bores 140 in ramped carriages 108. In theillustrated embodiment, slots 142 may be formed in arms 138. Any numberof slots 142 may be formed in arms 138. In the illustrated embodiment,each of the arms 138 includes a pair of slots 142. In some embodiments,one of the slots 142 may be disposed in each arm 138 between the rampedcarriages 108 while the other of the slots 142 may be disposed betweenbase plate 136 and one of the ramped carriages 108. Plates 144 may besecured in each of the slots 142. In the illustrated embodiments, pins146 may secure plates 144 in slots 142. In some embodiments, plates 144may project from either end of slots 142. As best seen on FIG. 6, pins146 may extend through holes 145 in arms 138. While FIGS. 4-6 illustrateplates 144 as one-piece plates, each of plates 144 may be multi-piece.Additionally, each end of plates 144 may contain a notch 148 (best seenon FIG. 6).

In some embodiments, projection actuation bar 122 may be displacedrelative to endplates 102, 104 (e.g., shown on FIGS. 1-3) by rotation ofdrive nut 126. As best seen on FIG. 6, base plate 136 may contain athrough bore 150, which may be threadedly coupled to a threaded portion152 of an extension 153 from drive nut 126. In accordance with presentembodiments, rotation of drive nut 126 may cause projection actuationbar 122 to translate along longitudinal axis 116 of spacer. Because arms138 may extend through ramped carriages 108, rotational movement ofdrive nut 126 may cause translation of projection actuation bar 122 asramped carriages 108 prevent rotation of projection actuation bar 122.

In some embodiments, actuation frame subassembly 110 may comprise a pairof retainer blocks 124. Guide pins 134 may be disposed in retainerblocks 124. As illustrated, guide pins 134 may project from either endof retainer blocks 124. In some embodiments, guide pins 134 may beplaced in corresponding openings 125 in retainer blocks 124, as seen onFIG. 6. The retainer blocks 124 may each have a through bore 154. In theillustrated embodiment, one of the retainer blocks 124 may be disposedon extension 153 of drive nut, wherein plate 106 is disposed betweenthat particular retainer block 124 and ramped carriages 108. The otherretainer block 124 may be disposed at an opposite end of drivesubassembly 120 on the drive shaft 128, wherein ramped carriages andplate 106 may be disposed between the retainer blocks 124.

Turning now to FIGS. 7 and 8, drive subassembly 120 is illustrated inmore detail in accordance with embodiments of the present invention. Asillustrated, drive assembly 120 includes a drive nut 126 and a driveshaft 128. In the illustrated embodiment, drive shaft 128 includes athreaded portion 132. Drive shaft 128 may include a proximal end 156 anda distal end 158. Drive shaft 128 may further include a tool engagementportion 160 to which a tool may be connected for rotation of drive shaft128 such that ramped carriages 108 may be withdrawn or advanced. Asillustrated, the tool engagement portion 160 may be disposed at proximalend 156. In the illustrated embodiment, tool engagement portion 160 isin the form of a hexagonal opening, but it should be understood thatother tool engagement types or shapes may be used as would be understoodby those ordinary skill in the art.

With additional reference to FIG. 9, drive nut 126 may include a headportion 162 and an extension 152. As illustrated, extension 152 mayinclude a threaded portion 153. An insertion tool (not shown) maythreadably engage threaded portion 153 and thus engage spacer 100 sothat spacer 100 can be retained during insertion. In the illustratedembodiment, a threaded end 164 may extend from head portion 162 in anopposite direction from extension 152. A tool (not shown) may interactwith head portion 162 to cause rotation of drive nut 126 so thatprojection actuation bar 122 (e.g., shown on FIGS. 4-6) may be withdrawnor advanced. Embodiments of drive nut 126 may also include a throughbore 166. In some embodiments, drive nut may further include first ring168 and second ring 170, which may both be in the form of a c-ring orother suitable device. In some embodiments, first ring 168 and secondring 170 may be compressible. In the illustrated embodiment, first ring168 may be retained in a groove 172 (best seen on FIGS. 8 and 9) formedin extension 152. In the illustrated embodiment, second ring 170 may beretained in an internal groove 174 formed in through bore 166 (best seenon FIG. 9). Proximal end 156 of drive shaft 128 may be inserted intothrough bore 166. In some embodiments, second ring 170 may be disposedon groove 176 of drive shaft 128 during insertion into through bore 166and expand to engage internal groove 174, thus securing drive shaft 128in through bore 166.

With additional reference to FIG. 10, a cutaway view of one of theretainer blocks 124 is illustrated. As previously described, retainerblocks 124 may include a through bore 154. In the illustratedembodiment, through bore 154 includes an internal groove 176. First ring168 disposed on drive nut 126 may engage internal groove 176 to retainone of the retainer blocks 124 on extension 153 of drive nut 126.

Turning now to FIGS. 10 and 11, projection actuation bar 122 isillustrated in more detail in accordance with present embodiments. Insome embodiments, projection actuation bar 122 may comprise base plate136 and arms 138. In the illustrated embodiment, base plate 136 may bein the form of a rectangular block with a proximal facing surface 178and a distal facing surface 180. A through bore 150 may be formed inbase plate 136 that extends from proximal facing surface 178 to distalfacing surface 180. In some embodiments, through bore 150 may containthreads 182, as illustrated on FIGS. 10 and 11. As best seen on FIG. 6,threaded portion 152 of drive nut 120 may threadingly engage threads 182of through bore 150 such that rotation of drive nut 120 causesprojection actuation bar 122 to translate along the longitudinal axis116 of spacer 100. As illustrated, through bore 150 may be locatedgenerally in the center of proximal facing surface 178, but through bore150 may be placed in other suitable locations. In some embodiments, arms138 may extend from distal facing surface 180 of base plate 136. Arms138 may generally be parallel and opposed to one another. Asillustrated, rods 138 may be cylindrical in shape, but other suitableshapes may be used included those with rectangular, square, ellipticalor otherwise formed cross-sections. In the illustrated embodiments,slots 142 may be formed in arms 138. Slots 142 may extend vertically andgenerally perpendicular to the longitudinal axis of the arms 138. Asillustrated, a pair of slots 142 may be formed in each of the arms 138.In some embodiments, holes 145 may be formed in arms 138 that intersectslots 142. As illustrated, holes 145 may each extend horizontallythrough arms 138 to intersect slots 142.

Embodiments of endplates 102, 104 will now be described in more detailwith reference to FIGS. 13-15. The following description is for endplate102; however, it should be understood that endplates 102 and 104 may besymmetrical so the description may equally apply to endplate 104.Endplate 102 may have a proximal end 184 and a distal end 186. As bestseen on FIG. 14, endplate 102 may further comprise an outer facingsurface 188 connecting proximal end 184 and distal end 186. Asillustrated, lateral sides 190 may extend downwardly from outer facingsurface 188. In some embodiments, expansion ramps 106 may be formed inlateral sides 190. As illustrated, each of the expansion ramps 106 maycomprise a pair of expansion ramps 106. The expansion ramps 106 may beat an incline with respect to longitudinal axis 116 of spacer 100. Itshould be understood that the number, spacing, incline, and arrangementof expansion ramps 106 may vary as desired for a particular application.By way of example, expansion ramps 106 and/or ramped carriages 108 maybe of differing height within spacer 100, whereby endplates 102, 104 maymutually separate at different rates at distal and proximal ends 112,114, whereby an angular disposition of adjacent bones may be changed,for example to correct lordosis or scoliosis. As previously described,ramped carriages 108 (e.g., FIG. 1) may engage expansion ramps 106. Insome embodiments, each of lateral sides 190 may also have an arm housing194 formed therein in which arms 138 (e.g., FIG. 11) of projectionactuation bar 122 may be disposed. In some embodiments, each of lateralsides 190 may also have cutouts 196. Cutouts 196 may be sized to receiveramped carriages 108. In the illustrated embodiment, expansion ramps 106may be formed in cutouts 196. In some embodiments, endplate 102 mayfurther comprise a cutout 198 in proximal end. Cutout 198 may be sizedto receive extension 153 of drive nut 120.

In some embodiments, endplate 102 may further comprise a through opening192. The through opening 192, in an exemplary embodiment, may be sizedto receive bone graft or similar bone growth inducing material andfurther allow the bone graft or similar bone growth inducing material tobe packed in a central opening 194 in actuation frame subassembly 110.

Endplates 102, 104 may additionally, or alternatively, be resilient, sothat they may conform to bony surfaces, forming a more stable supportplatform. Accordingly, endplates 102, 104 can be fabricated from apolymeric material, a naturally resilient material, or a resilientmetal, for example a shape memory alloy, or any other resilientbiocompatible material of sufficient strength and durability forseparating bones within the body.

As illustrated in FIG. 14, upper facing surface 188 of endplate 102 maybe flat and generally planar to allow the upper facing surface 188 toengage with the adjacent vertebral body. In alternative embodiments (notshown), upper facing surface 188 can be curved convexly or concavely toallow for a greater or lesser degree of engagement with the adjacentvertebral body. It is also contemplated that the upper facing surface188 can be generally planar but includes a generally straight rampedsurface or a curved ramped surface. The ramped surface may allow forengagement with the adjacent vertebral body 2 in a lordotic fashion.Turning back to FIG. 14, in an exemplary embodiment, the upper facingsurface 188 includes texturing 198 to aid in gripping the adjacentvertebral bodies. Although not limited to the following, the texturingcan include teeth, ridges, friction increasing elements, keels, orgripping or purchasing projections.

With reference now to FIGS. 16 and 17, an endplate subassembly 200 isillustrated in more detail in accordance with embodiments of the presentinvention. In some embodiments, endplate subassembly 200 may comprise anendplate 102 and body tissue engaging projection subassemblies 202.While FIGS. 16 and 17 illustrated endplate 102, it should be understoodthat the description herein with respect to endplate subassembly 200should apply equally to both of the endplates 102, 104. As best seen onFIGS. 16 and 17, compartments 204 may be formed in lateral sides 190.Compartments 204 may each be sized and configured to hold one of thebody tissue engaging projection subassemblies 202. The lateral sides 190may include holes 206. Pivot pins 208 may pass through the holes 206 topivotally couple the body tissue engaging projection subassemblies 202in compartments 204. The pivot pins 208 may define a pivot axis aboutwhich the body tissue engaging projection subassemblies 202 may berotated. While the pivot pins 208 for each of the body tissue engagingprojection subassemblies 202 is shown as being comprised of two or moreparts, it should be understood that the pivot pins 208 may comprise moreor less than two parts, for example, unitary pins may be used.

Embodiments of the body tissue engaging projection subassemblies 202will now be described in more detail with respect to FIGS. 18-19. In theillustrated embodiment, tissue engaging projection assembly 202 includesbase 210 and projection member 212. In some embodiments, projectionmember 212 may comprise a tissue engaging end 214 and a stop 216.Embodiments may further include post 218 that interconnects tissueengaging end 214 and stop 216. While tissue engaging end 214 is show inthe form of a conical spike, it should be understood that differentshaped tissue engaging ends may be used, including pyramid shaped endsand other pointed protrusions. In operation, the tissue engaging end 214may engage an adjacent vertebral body to stabilize the spacer 100. Inthe illustrated embodiment, stop 216 is in the form of a ball. However,differently shaped stops may be used that may be suitable for securingprojection member 212 to base 210.

With additional reference to FIG. 20, base 210 of tissue engagingprojection subassembly 202 will now be described in more detail inaccordance with embodiments of the present invention. In the illustratedembodiment, base 210 may comprise an outward facing surface 220 and aninward facing surface 222. In some embodiments, outward facing surface220 and inward facing surface 222 may extend between first end 224 andsecond end 226. A channel 228 may be formed in base 210. Channel 228 mayextend from outward facing surface 220 to inward facing surface 222. Asloping edge 230 may extend around channel 228 at inward facing surface222. As illustrated, channel 228 may be generally u-shaped and extend tofirst end 224. Post 218 of projection member 212 may be received inchannel 228. Stop 216 may be positioned on one side of base 210 whiletissue engaging end 214 may be positioned on the other side of base 210.In this manner, projection member 212 may be pivotally coupled to base210. At second end 226, base 210 may comprise a cylindrical-shapedsection 232 in which an opening 234 is formed for receiving a pivot pin208 (e.g., shown on FIG. 16). Opening 234 may form a pivot point aboutwhich base 210 may pivot. As best seen on FIG. 20, base 210 may furtherinclude a downward projection 236. Downward projection 236 may engageplate 144 of projection actuation bar 122 (e.g., shown on FIG. 6).

With reference now to FIGS. 21 and 22, assembly of actuation framesubassembly 110 to endplate subassembly 200 is illustrated in accordancewith embodiments of the present invention. In some embodiments,actuation frame subassembly 110 may be positioned in endplatesubassembly 220. Embodiments may include disposing ramped carriages 108in cutouts 196 of endplate 102 such that ramped carriages 108 engagelift ramps 150. Additionally, actuation frame subassembly 110 may bepositioned such that plates 144 of projection actuation bar 122 mayengage downward projections 236 of tissue engaging projectionsubassemblies 202.

Referring now to FIGS. 1-3 and 23-32, operation of spacer 100 will nowbe described in accordance with example embodiments. FIGS. 1, 23, and 24illustrate embodiments of spacer 100 in a collapsed configuration. FIGS.2 and 25-28 illustrate embodiments of spacer 100 in an expandedconfiguration with tissue engaging projection subassemblies 202retracted. FIGS. 3 and 29-32 illustrate embodiments of spacer 100 in anexpanded configuration with tissue engaging projection subassemblies 202deployed.

In operation, spacer 100 may be inserted between vertebral bodies whenin a collapsed or non-expanded state, as illustrated on FIGS. 1, 23, and24. In some embodiments, spacer 100 may be inserted from a lateralapproach to the spine. In some embodiments, an insertion tool (notshown) may threadably engage threaded portion 153 of drive nut 126 andthus engage spacer 100 so that spacer 100 can be retained duringinsertion. After insertion, in some embodiments, a tool (not shown) mayengage tool engagement portion 160 (best seen on FIG. 8) of drive shaft128. While tool engagement portion 160 is obstructed from view on FIGS.1, 23, and 24, in some embodiments, tool engagement portion 160 may beaccessed via through bore 166 of drive nut 126. With additionalreference to FIGS. 2 and 25-28, the tool may be used to rotate driveshaft 128 such that ramped carriages 108 may be withdrawn or advanced tocause expansion ramps 106 to slide along ramped carriages 108, therebymoving endplates 102, 104 such that a height of spacer 100 may beincreased. In this manner, spacer 100 may be moved from a collapsedconfiguration (e.g., shown in FIGS. 1, 23, and 24) to an expandedconfiguration (e.g., shown in FIGS. 2 and 25-28). In some embodiments,the tissue engaging projection subassemblies 202 may be retracted duringinsertion and expansion of spacer 100. With additional reference toFIGS. 3 and 29-32, deployment of tissue engaging subassemblies 202 willnow be described. In some embodiments, a tool (not shown) may be engagedwith head portion 162 of drive nut 126. The tool may be used to rotatedrive nut 126 causing advancement or retraction of projection actuationbar 122. As projection actuation bar 122 is advanced or retracted,plates 144 (e.g., coupled to arms 138 of projection actuation bar 122)should engage tissue engaging subassemblies 202 to cause projectionmembers 212 to extend through endplates 102, 104. Because movement oftissue engaging subassemblies 202 is restrained in compartments 204(e.g., shown on FIGS. 16 and 17), tissue engaging subassemblies 202should pivot outward from spacer 100 when engaged by plates 144. In thismanner, tissue engaging subassemblies 202 may be deployed afterinsertion and expansion of spacer 100, in accordance with exampleembodiments.

In some embodiments, spacer 100 may enable a continuous expansion andretraction over a range of displacements according to predetermineddimensions of a specific spacer design. This provides the ability todistract vertebral bodies or other bones to a desired height orseparation. Endplates 102, 104 can be shaped to form planes or surfaceswhich converge relative to each, to provide for proper lordosis, and canbe provided with through openings 192 (e.g., shown on FIGS. 13 and 14)through which bone may grow, and into which bone graft material may beplaced. In some embodiments, spacer 100 may be used to distract, orforce bones of a joint apart, or may be used to maintain a separation ofbones created by other means, for example by a retractor. Endplates 102,104 may additionally be curved to conform to the surface of body tissue,for example the surface of cortical bone, of the vertebra to becontacted, for improved fixation and load bearing.

In some embodiments, spacer 100 may be fabricated using anybiocompatible materials known or hereinafter discovered, havingsufficient strength, flexibility, resiliency, and durability for thepatient, and for the term during which the device is to be implanted.Examples include but are not limited to metal, such as, for exampletitanium and chromium alloys; stainless steel, polymers, including forexample, PEEK or high molecular weight polyethylene (HMWPE); andceramics. There are many other biocompatible materials which may beused, including other plastics and metals, as well as fabrication usingliving or preserved tissue, including autograft, allograft, andxenograft material. Portions or all of the spacer 100 may be radiopaqueor radiolucent, or materials having such properties may be added orincorporated into the spacer 100 to improve imaging of the device duringand after implantation. Any surface or component of a spacer 100 may becoated with or impregnated with therapeutic agents, including bonegrowth, healing, antimicrobial, or drug materials, which may be releasedat a therapeutic rate, using methods known to those skilled in the art.

In some embodiments, spacer 100 may be formed using titanium, or acobalt-chrome-molybdenum alloy, Co—Cr—Mo, for example as specified inASTM F1537 (and ISO 5832-12). The smooth surfaces may be plasma sprayedwith commercially pure titanium, as specified in ASTM F1580, F1978,F1147 and C-633 (and ISO 5832-2). Alternatively, part or all of spacers100 may be formed with a polymer, for example ultra-high molecularweight polyethylene, UHMWPE, for example as specified in ASTM F648 (andISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark of Invibio LtdCorp, United Kingdom) may be used for one or more components of thedisclosed spacers 100. For example, polymeric portions can be formedwith PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with present embodiments, spacer 100 may be provided invarious sizes to best fit the anatomy of the patient. Components ofmatching or divergent sizes may be assembled during the implantationprocedure by a medical practitioner as best meets the therapeutic needsof the patient, the assembly inserted within the body using an insertiontool. In some embodiments, spacer 100 may also be provided with anoverall angular geometry, for example an angular mating disposition ofendplates, to provide for a natural lordosis, or a corrective lordosis,for example of from 0° to 12° for a cervical application, although muchdifferent values may be advantageous for other joints. Lordotic anglesmay also be formed by shaping one or both endplates to have relativelynon-coplanar surfaces.

In some embodiments, expanded height of spacer 100 for use in thecervical vertebrae, for example, may typically range from 7 mm to 12 mm,but may be larger or smaller, including as small as 5 mm, and as largeas 16 mm, although the size is dependent on the patient, and the jointinto which spacer 100 may be implanted. A spacer 100 may be implantedwithin any level of the spine, and may also be implanted in other jointsof the body, including joints of the hand, wrist, elbow, shoulder, hip,knee, ankle, or foot.

In some embodiments, a single spacer 100 may be used, to providestabilization for a weakened joint or joint portion. Alternatively, acombination of two, three, or more of any of spacer 100 may be used, ata single joint level, or in multiple joints. Moreover, implants of thedisclosure may be combined with other stabilizing means.

In some embodiments, a spacer 100 may be fabricated using material thatbiodegrades in the body during a therapeutically advantageous timeinterval, for example after sufficient bone ingrowth has taken place.Further, implants of the disclosure are advantageously provided withsmooth and or rounded exterior surfaces, which reduce a potential fordeleterious mechanical effects on neighboring tissues.

In some embodiments, a spacer 100 may be provided to be support adjacentvertebrae during flexion/extension, lateral bending, and axial rotation.In one embodiment, spacer 100 is indicated for spinal arthroplasty intreating skeletally mature patients with degenerative disc disease,primary or recurrent disc herniation, spinal stenosis, or spondylosis inthe lumbosacral spine (LI-SI). The surgery to implant spacer 100 may beperformed through an Anterior, Anterolateral, Posterolateral, Lateral,or any other approach.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations may be made herein without departing from the spirit andscope of the invention as defined by the appended claims

What is claimed is:
 1. A spacer for separating bones of a joint, thespacer comprising: a first endplate configured to engage a first bone ofthe joint, and comprising a ramped surface; a tissue engagingsubassembly disposed in a compartment of the first endplate; a secondendplate configured to engage a second bone of the joint; and a framesubassembly that extends between the first endplate and the secondendplate, wherein the frame subassembly comprises: a drive nut, a driveshaft coupled to the drive nut, a ramped carriage coupled to the driveshaft, wherein the ramped carriage comprises a ramped surface operableto engage the ramped surface of the first endplate, and an actuation barcoupled to the drive nut comprising a plate operable to engage thetissue engaging subassembly.
 2. The spacer of claim 1, wherein thespacer is moveable from a collapsed position to an expanded position,wherein in the expanded position the spacer has a height that is greaterthan a height in the collapsed position.
 3. The spacer of claim 1,wherein the tissue engaging subassembly is movable from a retractedposition to a deployed position, wherein in the deployed position aprojection member of the tissue engaging portion extends through thefirst endplate.
 4. The spacer of claim 1, wherein the tissue engagingsubassembly comprises a base and projection member, wherein theprojection member comprises a tissue engaging end, a stop at an oppositeend from the tissue engaging end, and a post, wherein the post extendsthrough a channel in the base, wherein the stop secures the projectionmember to the base.
 5. The spacer of claim 4, wherein the projectionmember comprises a tissue engaging end in the form of a conical spike.6. The spacer of claim 4, wherein the base comprises a downwardprojection that extends from the base to engage the plate of theactuation bar.
 7. The spacer of claim 4, wherein the projection memberis pivotally coupled to the base.
 8. The spacer of claim 1, wherein thetissue engaging subassembly is pivotally coupled to the first endplate.9. The spacer of claim 1, wherein a proximal end of the drive shaft isretained in a through bore of the drive nut.
 10. The spacer of claim 1,wherein the ramped carriage is threadingly engaged with the drive nut.11. The spacer of claim 1, wherein the drive nut comprises a headportion, an extension from the head portion, the extension having athreaded portion, wherein the actuation bar is threadingly engaged withthe threaded portion of the extension.
 12. The spacer of claim 11,wherein the actuation bar comprises a base plate having a through borethrough which the extension of the drive nut extends, and a pair of armsthat extend from the drive nut toward a distal end of the spacer. 13.The spacer of claim 11, wherein the arms of the actuation bar extendthrough the ramped carriage.
 14. The spacer of claim 11, wherein theplate operable to engage the tissue engaging subassembly is disposed ina slot in one of the arms of the actuation bar.
 15. A spacer forseparating bones of a joint, the spacer comprising: a first endplateconfigured to engage a first bone of the joint, wherein the firstendplate comprises a pair of spaced first endplate ramped surfaces; afirst pair of tissue engaging subassemblies, wherein each of the tissueengaging subassemblies are pivotally coupled to the first endplate; asecond endplate configured to engage a second bone of the joint, whereinthe second endplate comprises a pair of spaced second endplate rampedsurfaces; a second pair of tissue engaging subassemblies, wherein eachof the tissue engaging subassemblies are pivotally coupled to the firstendplate; and a frame subassembly that extends between the firstendplate and the second endplate, wherein the frame subassemblycomprises: a drive nut at a proximate end of the spacer, wherein thedrive nut comprises a head portion and an extension, wherein theextension comprises a threaded portion; a drive shaft extending from thedrive nut towards a distal end of the spacer, wherein a proximal end ofthe drive shaft is retained in a through bore of the drive nut. a pairof ramped carriages that are spaced and threadingly coupled to the drivenut, wherein each of the ramped carriages comprises ramped surfacesoperable to engage the second endplate ramped surfaces and the secondendplate ramped surfaces; and an actuation bar coupled to the driveshaft comprising a base plate threadingly coupled to the threadedportion of the drive nut, a pair of opposing arms that extend from thebase plate toward a distal end of the spacer, the opposing armsextending through the ramped carriages, and plates disposed in spacedslots formed in each of the opposing arms of the actuation bar, whereinthe plates are operable to engaging the first pair of tissue engagingsubassemblies and the second pair of tissue engaging subassemblies. 16.A method of separating bones of a joint, comprising: inserting a spacerbetween bones of the joint; rotating a drive shaft of the spacer tocause translation of at least ramped carriage disposed on the driveshaft, wherein the at least one ramped carriage slides along at leastone ramped surface of a first endplate of the spacer to cause the firstendplate to move in a direction away from a second endplate of thespacer; and rotating a drive nut of the spacer to cause translation of abar subassembly disposed between the first endplate and the secondendplate such that at least one plate coupled to the frame engages atleast one tissue engaging subassembly to cause the at least one tissueengaging subassembly to deploy through the first endplate.
 17. Themethod of claim 16, wherein a base of the at least one tissue engagingsubassembly pivots about a pivot pin securing the at least one tissueengaging subassembly to the first endplate.
 18. The method of claim 16,wherein a tissue engaging end of the at least one tissue engagingsubassembly pivots about the base of the at least one tissue engagingsubassembly.
 19. The method of claim 16, wherein the drive shaft isretained in a through bore of the drive nut.
 20. The method of claim 16,wherein arms of the bar subassembly extend through the at least oneramped carriage.